Reciprocating power tool having a counterbalance device

ABSTRACT

A reciprocating power tool that includes a drive system having a first driven gear that includes a spindle counterbalance weight and a second driven gear that includes a spindle counterbalance weight. The first driven gear and the second driven gear rotate in opposite directions about an axis of rotation in response to rotation of a driving gear by a motor. The power tool further includes a spindle having a longitudinal axis and a first end that is configured to support a tool element. The spindle is coupled to one of the first driven gear and the second driven gear by a scotch yoke mechanism to reciprocate the spindle with respect to a housing of the power tool along the longitudinal axis of the spindle in response to operation of the motor.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a continuation-in-part of co-pendingU.S. patent application Ser. No. 12/399,839, filed Mar. 6, 2009, whichclaims priority to U.S. Provisional Patent Application No. 61/034,816,filed Mar. 7, 2008, the entire contents of which are all herebyincorporated by reference.

BACKGROUND

The present invention relates to a reciprocating saw, and, moreparticularly, to a portable, battery powered reciprocating saw.

Reciprocating saws are used to cut a variety of objects made from avariety of materials, such as metal pipes, wood and dry wall. Acordless, compact reciprocating saw allows for cutting operations intight spaces or awkward angles for plumbing, electrical, remodeling andHVAC applications.

SUMMARY

In one embodiment, the invention provides a reciprocating power toolincluding a housing and a motor supported by the housing and having anoutput shaft. The motor is operable to rotate the output shaft. A drivesystem is coupled to the output shaft of the motor. The drive systemincludes a driving gear coupled to the output shaft for rotation withthe output shaft and a first driven gear having a spindle counterbalanceweight. The first driven gear is coupled to the driving gear such thatthe first driven gear is configured to rotate about an axis of rotationin a first direction in response to rotation of the driving gear by themotor. The drive system further includes a second driven gear having aspindle counterbalance weight. The second driven gear is coupled to thedriving gear such that the second driven gear is configured to rotateabout the axis of rotation in a second direction that is opposite thefirst direction in response to rotation of the driving gear by themotor. The power tool further includes a spindle having a longitudinalaxis and a first end that is configured to support a tool element. Thespindle is coupled to one of the first driven gear and the second drivengear by a scotch yoke mechanism to reciprocate the spindle with respectto the housing along the longitudinal axis of the spindle in response tooperation of the motor.

In another embodiment the invention provides a reciprocating sawincluding a housing and a motor supported by the housing and having anoutput shaft. The motor is operable to rotate the output shaft. A drivesystem is coupled to the output shaft of the motor. The drive systemincludes a driving gear coupled to the output shaft for rotation withthe output shaft and a first driven gear having a spindle counterbalanceweight. The first driven gear is coupled to the driving gear such thatthe first driven gear is configured to rotate about an axis of rotationin a first direction in response to rotation of the driving gear by themotor. A second driven gear having a spindle counterbalance weight iscoupled to the driving gear such that the second driven gear isconfigured to rotate about the axis of rotation in a second directionthat is opposite the first direction in response to rotation of thedriving gear by the motor. The saw further includes a spindle having afirst end, a second end, and a longitudinal axis that extends throughthe first end and the second end. A blade clamp is coupled to the firstend of the spindle and the blade clamp is configured to couple a sawblade to the spindle. A yoke is coupled to the second end of thespindle. The drive system further includes a pin coupled to one of thefirst driven gear and the second driven gear for rotation with the oneof the first driven gear and the second driven gear and the pin extendsinto the yoke to reciprocate the spindle with respect to the housingalong the longitudinal axis of the spindle in response to operation ofthe motor.

In another embodiment the invention provides a reciprocating saw thatincludes a housing and a handle configured for a user. The handleincludes a longitudinal axis defining a first axis of the saw. A switchis adjacent the handle and is operable by the user when the user gripsthe handle. A motor is supported by the housing and includes an outputshaft. The motor is operable to rotate the output shaft about alongitudinal axis of the output shaft that defines a second axis of thesaw. The output shaft is configured to rotate in response to operationof the switch by the user. The saw further includes a drive systemcoupled to the output shaft of the motor. The drive system includes adriving gear coupled to the output shaft for rotation with the outputshaft and a driven gear having a spindle counterbalance weight. Thedriven gear is coupled to the driving gear such that the driven gear isconfigured to rotate about an axis of rotation in a first direction inresponse to rotation of the driving gear by the motor. The saw furtherincludes a spindle having a first end, a second end, and a longitudinalaxis that extends through the first end and the second end. Thelongitudinal axis of the spindle defines a third axis of the saw. Ablade clamp is coupled to the first end of the spindle and the bladeclamp is configured to couple a saw blade to the spindle. The spindle iscoupled to the driven gear to reciprocate the spindle with respect tothe housing in response to rotation of the output shaft of the motor andeach of the first axis, the second axis, and the third axis are obliquewith respect to each of the other axes.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a portable battery-powered reciprocating sawaccording to an embodiment of the invention.

FIG. 1 a is a perspective view of the portable battery-poweredreciprocating saw shown in FIG. 1 with a blade and battery pack removed.

FIG. 2 is another perspective view of the portable reciprocating sawshown in FIG. 1 a.

FIG. 3 is a side view of the portable reciprocating saw shown in FIG. 1a.

FIG. 4 is another side view of the portable reciprocating saw shown inFIG. 1 a.

FIG. 5 is a front view of the portable reciprocating saw shown in FIG. 1a.

FIG. 6 is a rear view of the portable reciprocating saw shown in FIG. 1a.

FIG. 7 is a cross section view of the portable reciprocating saw shownin FIG. 1 a.

FIG. 8 is an exploded view of the portable reciprocating saw shown inFIG. 1 a.

FIG. 9 is a detailed view of a portion of the gear case and housing ofthe portable reciprocating saw shown in FIG. 1 a.

FIG. 10 is a side view of a portable battery-powered reciprocating sawaccording to another embodiment of the invention.

FIG. 11 is an exploded view of the saw shown in FIG. 10.

FIG. 12 is a cross section view of the saw shown in FIG. 10.

FIG. 13 illustrates a drive system of the saw of FIG. 10 with a spindleof the saw in an extended position.

FIG. 14 illustrates the drive system of FIG. 13 with the spindle in afirst intermediate position.

FIG. 15 illustrates the drive system of FIG. 13 with the spindle in aretracted position.

FIG. 16 illustrates the drive system of FIG. 13 with the spindle in asecond intermediate position.

FIG. 17 illustrates a drive system of a saw according to anotherembodiment of the invention.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

DETAILED DESCRIPTION

A portable hand tool 20 or a portable reciprocating saw is shown inFIGS. 1-9. In these constructions, the saw 20 is a battery-poweredreciprocating saw. In the illustrated constructions, the saw 20 ispowered by a power tool battery pack 25. The battery pack 25 may beconfigured to connect and power a variety of tools in addition to thereciprocating saw 20. In the construction shown, the battery pack 25 isa 12V lithium-ion battery pack. The pack 25 includes three (3) batterycells (not shown) connected in series. In other embodiments, the batterypack 25 may include fewer or more battery cells, such that the batterypack 25 is a 14.4-volt power tool battery pack, an 18-volt power toolbattery pack, or the like. Additionally or alternatively, the batterycells may have chemistries other than lithium-ion such as, for example,nickel cadmium, nickel metal-hydride, or the like. In still otherconstructions, the saw 20 may be a corded power tool. In otherembodiments, the power tool may be another hand-held power tool, suchas, for example, another type of reciprocating power tool, a drill, ascrewdriver, or other handheld power tool.

The saw 20 includes a housing 40. As shown in FIG. 8, the housing 40 hasa first housing portion 42 and a second housing portion 44. Each housingportion 42, 44 is formed of plastic; however, in some embodiments, thehousing portions 42, 44 may be formed of other materials. In theconstruction shown, bosses 330 are formed in both housing portions 42,44. Each boss 330 includes an aperture 332, and each aperture 332extends through each housing portion 42, 44. When the housing portions42, 44 are assembled, the apertures 332 from the first housing portion42 generally align with the apertures 332 from the second housingportion 44. In some constructions, the bosses 330 from the first housingportion 42 align with and are in physical contact with the bosses 330formed in the second housing portion 44. In other constructions, thebosses 330 may be adjacent to respective bosses 330, although not inphysical contact with each other. In some constructions, the bosses 330may be of the same height. In other constructions, the bosses 330 may beof different height, such that to engage with each other, bosses 330 onone of the housing portions 42, 44 extend further than the bosses 330 onthe other of the housing portions 42, 44 (e.g., beyond a interface linebetween the housing portions 42, 44).

The housing 40 defines a handle housing portion 45, a motor housingportion 50 and a gear case housing portion 55. The handle housingportion 45 includes at least one grip surface 48 for a user to grasp. Inthe illustrated constructions, the handle housing portion 45 can alsodefine a battery receiving portion 60 (FIGS. 2 and 6) for receiving thebattery pack 25. In other constructions, the battery receiving portion60 may be defined elsewhere within the housing 40. The motor housingportion 50 supports a motor 65 (FIGS. 7 and 8), and the gear casehousing portion 55 in turn supports a gear case 68 (FIGS. 7 and 8).

As shown in FIG. 1, the battery receiving portion 60 is configured as acavity. When the battery pack 25 is connected to the saw 20, the pack 25is inserted into the cavity 60 and substantially closes the cavity 60. Aterminal block 70 (FIG. 6) is positioned in the cavity 60. The terminalblock 70 includes a positive terminal 75, a negative terminal 80 and asense terminal 85. The terminals 75, 80 electrically connect the batterypack 25 to the motor 65. The sense terminal 85 electrically connects thebattery pack 25 to a monitoring circuit 105, which is discussed below.

As shown in FIGS. 2-4 and 7, a switch 90 is positioned on the handlehousing portion 45 for powering the saw 20. As illustrated, the switch90 is an on/off trigger switch. In other embodiments, the switch 90 maybe a variable speed trigger switch, a two speed trigger switch, a pushbutton or other actuator.

A fuel gauge 100 is positioned on the motor housing portion 50 justabove the handle housing portion 45, as shown in FIG. 4. The fuel gauge100 is activated and controlled by the monitoring circuit 105. Thecircuit 105 is positioned within the housing 40 and communicates withthe battery pack 25. The monitoring circuit 105 periodically senses thestate of charge of the battery pack 25 via the sense terminal 85 anddisplays the remaining state of charge to the user with a visualindication via the fuel gauge 100. For example, in the illustratedconstruction, the fuel gauge 100 includes four (4) LEDs. To display 100%state of charge remaining in the pack 25, the circuit 105 would activateall four (4) LEDs. To display 75% state of charge remaining, the circuit105 would activate three (3) LEDs. For 50% state of charge remaining,two (2) LEDs would be activated, and for 25% state of charge remaining,one (1) LED would be activated. To display 10% state of charge remainingor a low state of charge warning, one (1) LED would be flashing.

In the construction shown, the fuel gauge 100 is activated when the useractuates the switch 90. In other constructions, the fuel gauge 100 maybe activated when the user actuates a secondary switch (not shown), suchas a push button.

Referring to FIGS. 7-9, the gear case 68 encloses a drive system 205 forthe saw 20. In this construction, the drive system 205 is a scotch yokemechanism. The drive system 205 includes a driving gear 210, a drivengear 215, a pin 225 connected to the driven gear 215, and a yoke 230. Inthis construction, the driving gear 210 is a spiral bevel pinion and thedriven gear 215 is a spiral bevel gear. The yoke 230 is connected to aspindle assembly 235. The spindle assembly 235 includes a spindle shaft240 and a blade clamp 260. As shown in FIG. 1, a tool element 250, suchas a blade, is coupled to the spindle shaft 240 via the blade clamp 260.In the construction shown, the blade clamp 260 includes the blade clampassembly shown and described in U.S. Pat. No. 6,725,548, entitled“Keyless Blade Clamp Mechanism” and issued Apr. 27, 2004, the contentsof which are hereby incorporated by reference. The blade clamp 260 canalso be configured to accept a variety of reciprocating saw blades, jigsaw blades and/or hack saw blades.

In operation, the pinion 210 is coupled directly to the output shaft ofthe motor 65. As the output shaft rotates, the pinion 210 rotates andengages teeth of the spiral bevel gear 215 to rotate the gear 215. Asthe spiral bevel gear 215 rotates, the pin 225 coupled to the gear 215also rotates. The yoke 230 includes a shaft 245 that surrounds the pin225 of the gear 215. Thereby, the yoke 230 translates back and forth dueto the pin 225 rotating within the shaft 245. The yoke 230 in turntranslates the spindle 240 in the desired reciprocating motion.

The gear case 68 also includes a first case portion 305 and a secondcase portion 310. In the construction shown, the gear case portions 305,310 are metal cases. When assembled, gear case portions are secured viafasteners 315. In the construction shown, each portion 305, 310 includesone or more tabs or hoops 320. Each tab 320 includes an aperture 325that extends through the tab 320, such that the apertures 325 align withand/or receive the bosses 330 formed in the housing portions 42, 44. Inother constructions, the tabs or hoops 320 can be positioned on just onegear case portion, such as, for example, the first case portion 305, butnot positioned on the other gear case portion, such as, for example, thesecond case portion 310. In further constructions, the tabs 320 can beformed on each gear case portion 305, 310. However, the tabs 320positioned on the first case portion 305 may not align with the tabs 320positioned on the second case portion 310. In this construction, thetabs 320 positioned on the first case portion 305 will only align withsome of the bosses 330, while the tabs 320 positioned on the second caseportion 310 will only align with the remaining bosses 330. In stillfurther constructions, the tabs 320 can be configured in a differentshape or manner.

As shown in FIG. 9, when the saw 20 is assembled, each of the bosses 330formed in the housing portions 42, 44 align with one of the apertures325 of the respective tab 320 formed in the gear case 68. Further, eachof the bosses 330 formed in the first housing portion 42 substantiallyalign in the tabs 320 with the bosses 330 formed in the second housingportion 44. The bosses 330 at least partially extend through the tabs320, such that the tab 320 surrounds a portion of at least one of thebosses 330. In some constructions, the bosses 330 from each housingportion 42, 44 contact each other within the tab 320. However, in otherconstructions, the bosses 330 from each housing portion 42, 44 may beadjacent, although not in physical contact, with each other. In otherconstructions, the bosses 330 may be of different height, such that toengage with each other, bosses 330 on one of the housing portions 42, 44extend further than the bosses 330 on the other of the housing portions42, 44.

Fasteners 340 are inserted into the bosses 330 to couple the firsthousing portion 42 to the second housing portion 44 and further securethe gear case 68 within the housing 40. Since the fasteners 340 residewithin the bosses 330, the fasteners 340 are electrically isolated fromthe gear case 68, including the drive system 205 and spindle shaft 240that are contained in the gear case 68, and thereby the gear case 68 iselectrically isolated within the housing 40 and from the rest of saw 20.

The saw 20 also includes a shoe assembly 350. In the construction shown,the shoe assembly 350 is a fixed shoe assembly. The shoe assembly 350includes a front surface or plate 360 which engages or rests on aworkpiece. As shown in FIGS. 3, 4 and 7, the front surface 360 isslightly curved outward from the saw 20, or non-planar. The frontsurface 360 is curved such that any three points on the front surface360 lying in a plane parallel to a center plane (coplanar with axis 420)of saw 20 defines an arc or radius of curvature of approximately 170 mm.In other constructions (not shown), the plate 360 may have a radiusgreater than or less than 170 mm The front plate 360 also defines anopening 365 for the saw blade 250 to pass through. The shoe assembly 350further includes a top portion 395 coupled to the top of the frontsurface 360 and lying outside of the 170 mm arc. The shoe assembly 350also includes two connecting members 370 for connecting the shoeassembly 350 to the housing 40. In other constructions (not shown), theshoe assembly 350 may be an adjustable shoe assembly or a pivoting shoeassembly.

As shown in FIG. 7, the battery pack 25 is inserted into the batterycavity 60 of the saw 20 along a handle axis 400, which also defines abattery insertion axis. The motor 65 is positioned within the housing 40and defines a longitudinal motor axis 410 along a length of the motor65. The gear case is also positioned along the motor axis 410. Thespindle 240 and the saw blade 250 are positioned along a longitudinalspindle axis 420 defined along a length of the spindle 240 and saw blade250. The reciprocating motion of the spindle 240 translates back andforth along the spindle axis 420.

The axes 400, 410, 420 are positioned such that each axis 400, 410, 420is oblique, or not otherwise perpendicular and/or parallel with respectto the other axes. More specifically, the handle axis 400 is positionedat an angle a with respect to the motor axis 410, the motor axis 410 ispositioned at an angle θ with respect to the spindle axis 420, and thespindle axis 420 is positioned at an angle β with respect to the handleaxis 400. In some embodiments, each of the axes 400, 410, 420 may beeither non-parallel or non-orthogonal with respect to each of the otheraxes 400, 410, 420.

In the illustrated construction and referring to FIG. 7, each of theaxes 400, 410, 420 is oblique with respect to the other axes 400, 410,420. Angle α is an angle defined between the handle axis 400 and themotor axis 410 and is in a range of approximately 75 degrees to 95degrees. In the illustrated embodiment, angle α is 85 degrees. In stillother contructions, angle a may be greater than 95 degrees or less than75 degrees. Angle θ is an angle defined between the motor axis 410 andthe spindle axis 420 and is in a range of approximately 110 degrees to130 degrees. In the illustrated construction, angle θ is approximately120 degrees. In other constructions, angle θ may be greater than 130degrees or less than 110 degrees. Angle β is an angle defined betweenthe handle axis 400 and the spindle axis 420 and is in a range ofapproximately 150 degrees to 170 degrees. In the illustratedconstruction, angle β is approximately 161.7 degrees. In otherconstructions, angle β is greater than 170 degrees or less than 150degrees.

The position of the axes, the size of the tool, and othercharacteristics are designed for optimal cutting application for the saw20, including but not limited to PVC cutting, dry wall cutting, lightmetal cutting, EMT or thin wall conduit cutting and the like. Forexample, the orientation of motor 65 along motor axis 410 allows the saw20 to be more compact by reducing the overall length of saw 20 ascompared to the length of a conventional saw. Saw 20 is alsoergonomically designed such that the longitudinal axis 400 is positionedfor optimal user operation related to handle grip location and angle forperforming a cutting operation.

FIGS. 10-16 illustrate a reciprocating power tool 520 according toanother embodiment of the invention. The reciprocating power tool 520,which is a reciprocating saw in the illustrated embodiment, includesfeatures similar to the saw 20 of FIGS. 1-9. Accordingly, components ofthe saw 520 illustrated in the embodiment of FIGS. 10-16 that aresimilar to components of the saw 20 illustrated in the embodiment ofFIGS. 1-9 have been given similar reference numbers, plus 500. Also,only differences between the saw 20 of FIGS. 1-9 and the saw 520 ofFIGS. 10-16 will be discussed in detail below and it should beunderstood that the features and alternative constructions of the saw 20discussed above could also be applied to the saw 520 of FIGS. 10-16.

Referring to FIG. 10, the illustrated saw 520 is powered by a batterypack 525, which is an 18 Volt lithium-ion battery back in oneembodiment. In other embodiments, other types of batteries, such as thebatteries described above with regard to the saw 20 may be used. In yetother embodiments, the saw 520 may be a corded power tool. Furthermore,while the illustrated reciprocating power tool 520 is a reciprocatingsaw, in other embodiments, other types of reciprocating power tools maybe used.

Referring to FIG. 11, the saw 520 includes a housing 540 having a firsthousing portion 542 and a second housing portion 544. The housing 540defines a handle portion 545 of the saw 520, and the handle portion 545defines a longitudinal axis 900 (FIG. 12). A motor 565 is supported bythe housing 540 and includes an output shaft 566. The motor 565 isoperable to rotate the output shaft 566 about a longitudinal axis 910 ofthe shaft 566 in response to operation of a switch 590 (FIG. 10) by auser.

The saw 520 further includes a drive system 705 coupled to the outputshaft 566 of the motor 565. The drive system 705 converts rotation ofthe output shaft 566 to reciprocation of a tool element 750 (FIG. 10),which is a saw blade in the illustrated embodiment. The drive system 705includes a driving gear or pinion 710 that is coupled to the shaft 566for rotation with the shaft 566. In the illustrated embodiment, thepinion 710 is a spiral bevel gear having 8 teeth, but in otherembodiments, the pinion has more or less than 8 teeth and other types ofgears may be used.

The drive system 705 further includes a first driven gear 715A and asecond driven gear 715B. The driven gears 715A, 715B engage the pinion710 such that rotation of the pinion 710 rotates the gears 715A, 715Babout an axis 720. In the illustrated embodiment, the driven gears 715A,715B are identical so that only one part is manufactured and the part isused as either driven gear 715A or 715B. Also, in the illustratedembodiment, the driven gears 715A, 715B are spiral bevel gears eachhaving 54 teeth. In other embodiments, the gears 715A, 715B have more orless than 54 teeth, and other types of gears may be used.

The gears 715A, 715B both include a spindle counterbalance weight 722A,722B, respectively. The counterbalance weights 722A, 722B offset thecenter of gravity of the respective gear 715A, 715B so that the centerof gravity of the gear 715A, 715B is not at the axis of rotation 720,but rather the center of gravity of each gear 715A, 715B is radiallyoffset from the axis 720 by the mass of the respective counterbalanceweight 722A, 722B. The counterbalance weights 722A, 722B reducevibrations during operation of the saw 520, which will be discussed inmore detail below. The illustrated counterbalance weights 722A, 722B areintegrally formed with the gears 715A, 715B, respectively, such as byforging, casting, sintering, milling, machining, and the like.

The saw 520 further includes a spindle 735. The illustrated spindle 735includes a first portion 740 and a second portion 742 that is coupled tothe first portion 740. The first portion 740 of the spindle 735 definesa first end 744 of the spindle 735 and the first portion 740 includes acylindrical portion 746. A blade clamp 760 is coupled to the first end744 of the spindle 735. The blade clamp 760, as discussed above withregard to the saw 20, is configured to attach the saw blade 750 (FIG.10) to the spindle 735.

The second portion 742 of the spindle 735 includes a threadedcylindrical portion 754, a flat sidewall portion 756, and a yoke 730.The threaded cylindrical portion 754 is used to couple the first portion740 of the spindle 735 to the second portion 740. As illustrated in FIG.12, the threaded portion 754 of the second portion 742 is receivedwithin the first portion 740 of the spindle 735 to couple the first andthe second portions 740, 742. As best seen in FIG. 13, the flat sidewallportion 756 reduces the outer dimensions of the spindle 735 so that thespindle 735 can fit between the gears 715A, 715B. Also, the relativelysmall distance between the flat sidewall portion 756 of the spindle 735and the gears 715A, 715B limits rotation of the spindle 735 about alongitudinal axis 920 of the spindle 735.

Referring to FIGS. 11 and 12, the illustrated yoke 730 is formed by anoval aperture that extends through the spindle 735. Accordingly, theyoke 730 is integrally formed with the spindle 735 as a singlecomponent. In other embodiments, the yoke may be alternatively formedwith the spindle, such as the yoke 230 of FIGS. 7 and 8 that is formedby the shaft 245.

With continued reference to FIGS. 11 and 12, the drive system 705further includes a pin 725. The pin 725 is received in an aperture 726of the first driven gear 715A so that the pin 725 rotates with thedriven gear 715A about the axis 720. Alternately, the pin 725 may becoupled for rotation with the second driven gear 715B that rotates in anopposite direction as the driven gear 715A. The pin 725 supports abearing 728, and the pin 725 extends into the yoke 730 to position thebearing 728 within the yoke 728 (FIG. 12). The bearing 728 rolls withinthe yoke 730 and reduces friction between the pin 725 and yoke 730 whenthe pin 725 rotates with the gear 715A.

Referring to FIG. 11, the saw 520 further includes a gear case 568having a first case portion 805 and a second case portion 810 thatenclose the drive system 705 to protect the drive system 705 from dust,debris, and the like. The gear case 568 includes a cylinder 812 (FIG.12) that receives the cylindrical portion 746 of the spindle 735 inorder to guide reciprocating movement of the spindle 735 along the axis920. The gear case 568 supports bearings 813 and 814. The bearing 813 iscoupled to the first driven gear 715A to facilitate rotation of the gear715A with respect to the gear case 568, and the bearing 814 is coupledto the second driven gear 715B to facilitate rotation of the gear 715Bwith respect to the gear case 568. As discussed above with regard toFIGS. 1-9, fasteners 815 couple the gear case portions 805, 810 togetherand the fasteners 840 couple the gear case 568 to the housing 540.

In operation, referring to FIGS. 10 and 13, a user grasps a handleportion 545 of the housing 540 and presses the switch 590, which causesthe motor 565 to rotate the output shaft 566 and the pinion 710 aboutthe axis 910. In the illustrated construction, the shaft 566 and thepinion 710 are rotated about the axis 910 in a direction that causes thefirst driven gear 715A to rotate in the direction of arrow 924 of FIG.13 (e.g., counterclockwise about the axis 720 as illustrated in FIG. 13)and the second driven gear 715B to rotate in the opposite direction orin the direction of arrow 926 of FIG. 13 (e.g., clockwise about the axis720 as illustrated in FIG. 13).

Rotation of the first driven gear 715A about the axis 720 causes the pin725 to also rotate about the axis 720. Rotation of the pin 725 aroundthe axis 720 reciprocates the spindle 735 with respect to the housing540 along the longitudinal axis 920 of the spindle 735. The spindle 735reciprocates in the directions of arrows 928 (FIGS. 13) and 930 (FIG.14) between an extended position (FIG. 13) and a retracted position(FIG. 15). The extended position of the spindle 735 (FIG. 13) is definedas the position of the spindle 735 when a distance 934A between thefirst end 744 of the spindle 735 and the axis of rotation 720 of thegears 715A, 715B is the greatest. The retracted position of the spindle735 (FIG. 15) is defined as the position of the spindle 735 when adistance 934B between the first end 744 of the spindle 735 and the axisof rotation 720 of the gears 715A, 715B is the lowest. Intermediatepositions are defined as any position of the spindle 735 between theextended position and the retracted position, and two intermediatepositions are illustrated in FIGS. 14 and 16.

The imbalanced gears 715A, 715B, caused by the spindle counterbalanceweights 722A, 722B, counterbalance a reciprocating mass of the spindle735, which is the blade clamp 760 (FIG. 12), and the saw blade 750 (FIG.10) (collectively hereinafter—“reciprocating mass”). For example,referring to FIG. 13, when spindle 735 is in the extended position, bothcounterbalance weights 722A, 722B are in a rearward position tocounterbalance the outward movement of the reciprocating mass in thedirection of arrow 928. As the pinion 710 continues to rotate, thereciprocating mass moves from the position illustrated in FIG. 13 inwardor in the direction of arrow 930 (FIG. 14) to the intermediate positionillustrated in FIG. 14. As the gear 715A rotates to move the spindle 735from the retracted position toward the intermediate position illustratedin FIG. 14, the counterbalance weight 722A rotates in the direction ofarrow 924 and from the position illustrated in FIG. 13 to the positionillustrated in FIG. 14. Meanwhile, the gear 715B rotates in the oppositedirection (direction of arrow 926) and the counterbalance weight 722Brotates in the direction of arrow 926 from the position illustrated inFIG. 13 to the position illustrated in FIG. 14. In the intermediateposition illustrated in FIG. 14, the counterbalance weight 722A is in anupper position and the counterbalance weight 722B is in a lowerposition. In the upper position, the counterbalance weight 722A isdirectly above the counterbalance weight 722B. The opposed positions ofthe counterbalance weights 722A, 722B in FIG. 14 balance any vibrationin the direction of arrows 938 and 940 (FIG. 14) caused by rotation ofthe counterbalance weights 722A, 722B and that are normal to thereciprocating axis 920.

Referring to FIG. 15, when the spindle 735 is in the retracted position,the counterbalance weights 722A, 722B are in a forward position tocounterbalance the inward movement of the reciprocating mass in thedirection of arrow 930. As the pinion 710 continues to rotate, thereciprocating mass moves from the position illustrated in FIG. 15outward or in the direction of arrow 928 to the intermediate positionillustrated in FIG. 16. The gear 715A rotates in the direction of arrow924 to move the spindle 735 from the retracted position (FIG. 15) towardthe intermediate position illustrated in FIG. 16. The rotation of thegear 715A causes the counterbalance weight 722A to move from theposition illustrated in FIG. 15 to the position illustrated in FIG. 16.Meanwhile, the pinion 710 causes the gear 715B to rotate in thedirection of arrow 926, which causes the counterbalance weight 722B tomove from the position illustrated in FIG. 15 to the positionillustrated in FIG. 16. In the intermediate position illustrated in FIG.16, the counterbalance weight 722A is in the lower position and thecounterbalance weight 722B is in the upper position. In the lowerposition, the counterbalance weight 722A is directly below thecounterbalance weight 722B. Again, the opposed positions of thecounterbalance weights 722A, 722B in FIG. 16 balance any vibration inthe direction of arrows 938 and 940 that are normal to the reciprocatingaxis 920 caused by rotation of the counterbalance weights 722A, 722B.

Accordingly, the counterbalance weights 722A, 722B reduce vibrationscaused by the reciprocating mass along the reciprocating axis 920.Meanwhile, the counterbalance weights 722A, 722B do not add additionalvibrations in directions normal to the axis 920 (e.g., the direction ofarrows 938, 940) because the gears 715A, 715B rotate in oppositedirections and one of the counterweights 722A or 722B is at leastpartially above the other counterweight 722B or 722A in the intermediatepositions of the spindle 735 to provide balance in the directions 938,940 (which are shown as vertical in FIGS. 13-16).

Furthermore, the saw 520 utilizes a scotch yoke mechanism that furtherreduces vibration normal to the axis 920 or in the direction of arrows938, 940. Together the pin 725, the yoke 730, and the gear 715A form aportion of the scotch yoke mechanism. A scotch yoke mechanism convertsrotational motion to linear motion of a slider or vice-versa. A scotchyoke mechanism is distinguishable from a slider crank mechanism. Aslider of a slider crank mechanism is connected to a crank via aconnecting rod. As the crank of the slider crank mechanism rotates, theconnecting rod travels in two directions along the longitudinal axis andin directions oblique to the longitudinal axis. For example, referringto FIGS. 13 and 14, if the drive system 705 used a slider crankmechanism, the spindle 735 would reciprocate along the longitudinal axis920 (direction of arrows 928, 930) and also oblique to the longitudinalaxis 920 (e.g., there would be movement of the spindle 735 in thedirections of arrows 938, 940). Reciprocation of the spindle 735 obliqueto or normal to the longitudinal axis 920 creates additional vibrationsin the direction of arrows 938, 940. These additional vibrations are notcreated by the scotch yoke mechanism of the saw 520 because the scotchyoke mechanism causes the spindle 735 to reciprocate only in thedirection of arrows 928, 930 that are parallel to the longitudinal axis920 and the spindle 735 does not reciprocate in directions that areoblique to or normal to the longitudinal axis 920.

Similar to the saw 20 of FIGS. 1-9, the axes 900, 910, and 920 of thesaw 520 of FIGS. 10-16 are orientated to reduce the overall length ofthe saw 520 as compared to the length of a conventional saw.

Referring to FIG. 12, the axes 900, 910, 920 are positioned such thateach axis 900, 910, 920 is oblique, or not otherwise perpendicular orparallel with respect to the other axes. More specifically, the handleaxis 900 is positioned at an angle a with respect to the motor axis 910,the motor axis 910 is positioned at an angle θ with respect to thespindle axis 920, and the spindle axis 920 is positioned at an angle βwith respect to the handle axis 900. In some embodiments, each of theaxes 900, 910, 920 may be either non-parallel or non-orthogonal withrespect to each of the other axes 900, 910, 920.

In the illustrated embodiment and referring to FIG. 12, each of the axes900, 910, 920 is oblique with respect to the other axes 900, 910, 920.Angle α is an angle defined between the handle axis 900 and the motoraxis 910 and is in a range of approximately 75 degrees to 95 degrees. Inthe illustrated embodiment, angle a is 85 degrees. In still otherembodiments, angle α may be greater than 95 degrees or less than 75degrees and could be in a range of approximately 30 degrees to 150degrees. Angle θ is an angle defined between the motor axis 910 and thespindle axis 920 and is in a range of approximately 110 degrees to 130degrees. In the illustrated construction, angle θ is approximately 120degrees. In other constructions, angle θ may be greater than 130 degreesor less than 110 degrees and could be in a range of approximately 30degrees to 150 degrees. Angle β is an angle defined between the handleaxis 900 and the spindle axis 920 and is in a range of approximately 150degrees to 170 degrees. In the illustrated embodiment, angle β isapproximately 156 degrees. In other embodiments, angle β is greater than170 degrees or less than 150 degrees and could be in a range of 100degrees to 175 degrees.

FIG. 17 illustrates a drive system 1005 of a saw according to anotherembodiment of the invention. The drive system 1005 of FIG. 17 can beused in the saw 520 of FIGS. 10-12 instead of the drive system 705 ofFIGS. 13-16. The drive system 1005 of FIG. 17 includes components thatare similar to the components of the drive system 705 of FIGS. 10-12.Therefore, like components of the drive systems 705 and 1005 have beengiven the same reference number and only the differences between thedrive systems 705 and 1005 will be discussed in detail below.

The drive system 1005 of FIG. 17 includes a spindle counterbalanceweight 1010 and the drive system 1005 does not include the second drivengear 715B of the drive system 705 of FIG. 13. Referring to FIG. 17, thespindle counterbalance weight 1010 includes a collar 1014, a relativelylarge lobe 1016 that extends radially from the collar 1014, and arelatively small lobe 1018 that extends radially from the collar 1014opposite the large lobe 1016. The collar 1014 is received within thebearing 814 (FIG. 11) to rotatably couple the counterbalance weight 1010to the first gear case portion 805. With continued reference to FIG. 17,the small lobe 1018 includes an aperture 1022 that receives a first end1024 of the pin 725. As best seen in FIG. 11, a second end 1026 of thepin 725 is received in the aperture 726 of the driven gear 715A. As bestseen in FIG. 17, the pin 725 extends through the yoke 730 to couple thedriven gear 715A and the spindle counterbalance weight 1010 such thatthe spindle counterbalance weight 1010 rotates about the axis 720 in thedirection of arrow 924 with the driven gear 715A.

In operation, the pinion 710 is rotated about the axis 910 in adirection that causes the driven gear 715A to rotate in the direction ofthe arrow 924 of FIG. 17 (e.g., counterclockwise about the axis 720 asillustrated in FIG. 17). Rotation of the driven gear 715A about the axis720 causes the pin 725 to also rotate about the axis 720. Therefore, thecounterbalance weight 1010 also rotates in the direction of arrow 924about the axis 720.

Rotation of the pin 725 around the axis 720 reciprocates the spindle 735along the longitudinal axis 920 of the spindle 735. The spindle 735reciprocates in the directions of arrows 928 and 930 between theextended position (FIG. 17) and the retracted position (see FIG. 15).

The imbalanced gear 715A having the counterbalance weight 722A and thecounterbalance weight 1010 having the large lobe 1016 counterbalance thereciprocating mass. For example, referring to FIG. 17, when spindle 735is in the extended position, both the counterbalance weight 722A and thelarge lobe 1016 are in the rearward position to counterbalance theoutward movement of the reciprocating mass in the direction of arrow928. Also, when the spindle 735 is in the retracted position, thecounterbalance weight 722A and the large lobe 1016 are in a forwardposition to counterbalance the inward movement of the reciprocating massin the direction of arrow 930. Accordingly, the counterbalance weight722A and the large lobe 1016 reduce vibrations caused by thereciprocating mass along the reciprocating axis 920.

Although the invention has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe scope and spirit of one or more independent aspects of the inventionas described.

1. A reciprocating power tool comprising: a housing; a motor supportedby the housing and having an output shaft, the motor operable to rotatethe output shaft; a drive system coupled to the output shaft of themotor, the drive system including, a driving gear coupled to the outputshaft for rotation with the output shaft, a first driven gear having aspindle counterbalance weight, the first driven gear coupled to thedriving gear such that the first driven gear is configured to rotateabout an axis of rotation in a first direction in response to rotationof the driving gear by the motor, a second driven gear having a spindlecounterbalance weight, the second driven gear coupled to the drivinggear such that the second driven gear is configured to rotate about theaxis of rotation in a second direction that is opposite the firstdirection in response to rotation of the driving gear by the motor, aspindle having a longitudinal axis and a first end configured to supporta tool element, and wherein the spindle is coupled to one of the firstdriven gear and the second driven gear by a scotch yoke mechanism toreciprocate the spindle with respect to the housing along thelongitudinal axis of the spindle in response to operation of the motor.2. The reciprocating power tool of claim 1, further comprising, a yokecoupled to the spindle, wherein the drive system further includes a pincoupled to one of the first driven gear and the second driven gear forrotation with the one of the first driven gear and the second drivengear, and wherein the pin is received within the yoke to reciprocate thespindle with respect to the housing along the longitudinal axis of thespindle in response to rotation of the one of the first driven gear andthe second driven gear.
 3. The reciprocating power tool of claim 2,wherein the spindle includes a second end opposite the first end, andwherein the yoke is integrally formed with the spindle as a singlecomponent and the yoke defines the second end of the spindle.
 4. Thereciprocating power tool of claim 1, wherein the spindle onlyreciprocates in directions parallel to the longitudinal axis of thespindle in response to operation of the motor.
 5. The reciprocatingpower tool of claim 4, wherein the spindle generally does notreciprocate in directions oblique to the longitudinal axis of thespindle in response to operation of the motor.
 6. The reciprocatingpower tool of claim 1, further comprising, a gear case substantiallyenclosing the drive system, the gear case having a cylinder, wherein thespindle includes a generally cylindrical portion received within thecylinder of the gear case to guide reciprocating movement of thespindle, and wherein the spindle further includes a generally flatsidewall portion positioned between the first driven gear and the seconddriven gear to limit rotation of the spindle about the longitudinal axisof the spindle.
 7. The reciprocating power tool of claim 1, wherein thespindle counterbalance weights of the first and the second driven gearsrotate with the first and the second driven gears, respectively, betweenan upper position, a forward position, a lower position opposite theupper position, and a rearward position opposite the forward position,wherein the spindle reciprocates between an extended position, aretracted position, a first intermediate position, and a secondintermediate position, wherein when the spindle is in the extendedposition, the spindle counterbalance weights of the first and the seconddriven gears are in the rearward positions, wherein when the spindle isin the retracted position, the spindle counterbalance weights of thefirst and the second driven gears are in the forward positions, whereinwhen the spindle is in the first intermediate position, the spindlecounterbalance weight of the first driven gear is in the upper positionand the spindle counterbalance weight of the second driven gear is inthe lower position, and wherein when the spindle is in the secondintermediate position, the spindle counterbalance weight of the firstdriven gear is in the lower position and the spindle counterbalanceweight of the second driven gear is in the upper position.
 8. Areciprocating saw comprising: a housing; a motor supported by thehousing and having an output shaft, the motor operable to rotate theoutput shaft; a drive system coupled to the output shaft of the motor,the drive system including, a driving gear coupled to the output shaftfor rotation with the output shaft, a first driven gear having a spindlecounterbalance weight, the first driven gear coupled to the driving gearsuch that the first driven gear is configured to rotate about an axis ofrotation in a first direction in response to rotation of the drivinggear by the motor, a second driven gear having a spindle counterbalanceweight, the second driven gear coupled to the driving gear such that thesecond driven gear is configured to rotate about the axis of rotation ina second direction that is opposite the first direction in response torotation of the driving gear by the motor, a spindle having a first end,a second end, and a longitudinal axis that extends through the first endand the second end; a blade clamp coupled to the first end of thespindle, the blade clamp configured to couple a saw blade to thespindle; and a yoke coupled to the second end of the spindle, whereinthe drive system further includes a pin coupled to one of the firstdriven gear and the second driven gear for rotation with the one of thefirst driven gear and the second driven gear, and wherein the pinextends into the yoke to reciprocate the spindle with respect to thehousing along the longitudinal axis of the spindle in response tooperation of the motor.
 9. The reciprocating saw of claim 8, wherein thespindle only reciprocates in directions parallel to the longitudinalaxis of the spindle in response to operation of the motor.
 10. Thereciprocating saw of claim 9, wherein the spindle generally does notreciprocate in directions oblique to the longitudinal axis of thespindle in response to operation of the motor.
 11. The reciprocating sawof claim 8, further comprising, a gear case substantially enclosing thedrive system, the gear case having a cylinder, wherein the spindleincludes a generally cylindrical portion received within the cylinder ofthe gear case to guide reciprocating movement of the spindle, andwherein the spindle further includes a generally flat sidewall portionpositioned between the first driven gear and the second driven gear tolimit rotation of the spindle about the longitudinal axis of thespindle.
 12. The reciprocating saw of claim 8, wherein the spindlecounterbalance weights of the first and the second driven gears rotatewith the first and the second driven gears, respectively, between anupper position, a forward position, a lower position opposite the upperposition, and a rearward position opposite the forward position, whereinthe spindle reciprocates between an extended position and a retractedposition, wherein a plurality of intermediate positions are definedbetween the extended position and the retracted position, wherein whenthe spindle is in the extended position, the spindle counterbalanceweights of the first and the second driven gears are in the rearwardpositions, wherein when the spindle is in the retracted position, thespindle counterbalance weights of the first and the second driven gearsare in the forward positions, and wherein when the spindle is in theplurality of intermediate positions, at least a portion of the spindlecounterbalance weight of one of the first and the second driven gears isabove the counter balance weight of the other of the first and thesecond driven gears.
 13. The reciprocating saw of claim 8, wherein thefirst driven gear and the second driven gear are substantiallyidentical.
 14. The reciprocating saw of claim 8, wherein the yoke isintegrally formed with the spindle as a single component.
 15. Areciprocating saw comprising: a housing; a handle configured for a user,the handle having a longitudinal axis defining a first axis of the saw;a switch adjacent the handle and operable by the user when the usergrips the handle; a motor supported by the housing and having an outputshaft, the motor operable to rotate the output shaft about alongitudinal axis of the output shaft that defines a second axis of thesaw, the output shaft configured to rotate in response to operation ofthe switch by the user; a drive system coupled to the output shaft ofthe motor, the drive system including, a driving gear coupled to theoutput shaft for rotation with the output shaft, a driven gear having aspindle counterbalance weight, the driven gear coupled to the drivinggear such that the driven gear is configured to rotate about an axis ofrotation in a first direction in response to rotation of the drivinggear by the motor; a spindle having a first end, a second end, and alongitudinal axis that extends through the first end and the second end,the longitudinal axis of the spindle defining a third axis of the saw;and a blade clamp coupled to the first end of the spindle, the bladeclamp configured to couple a saw blade to the spindle, wherein thespindle is coupled to the driven gear to reciprocate the spindle withrespect to the housing in response to rotation of the output shaft ofthe motor, and wherein each of the first axis, the second axis, and thethird axis are oblique with respect to each of the other axes.
 16. Thereciprocating saw of claim 15, wherein the first axis and the secondaxis define a first angle, the second axis and the third axis define asecond angle, and the third axis and the first axis define a thirdangle, and wherein the first angle is in a range of approximately 30degrees to 150 degrees, the second angle is in a range of approximately30 degrees to 150 degrees, and the third angle is in a range ofapproximately 100 degrees to 175 degrees.
 17. The reciprocating saw ofclaim 16, wherein the first angle is in a range of approximately 75degrees to 95 degrees, the second angle is in a range of approximately110 degrees to 130 degrees, and the third angle is in a range ofapproximately 150 degrees to 170 degrees.
 18. The reciprocating saw ofclaim 15, further comprising, a yoke coupled to the second end of thespindle, wherein the drive system further includes a pin coupled to thedriven gear for rotation with the driven gear, and wherein the pinextends into the yoke to reciprocate the spindle with respect to thehousing along the longitudinal axis of the spindle in response tooperation of the motor.
 19. The reciprocating saw of claim 18, whereinthe spindle only reciprocates in directions parallel to the longitudinalaxis of the spindle in response to operation of the motor.
 20. Thereciprocating saw of claim 15, wherein the driven gear is a first drivengear, the drive system further including a second driven gear having aspindle counterbalance weight, the second driven gear coupled to thedriving gear such that the second driven gear is configured to rotateabout the axis of rotation in a second direction that is opposite thefirst direction in response to rotation of the driving gear by themotor, wherein the spindle counterbalance weights of the first and thesecond driven gears rotate with the first and the second driven gears,respectively, between an upper position, a forward position, a lowerposition opposite the upper position, and a rearward position oppositethe forward position, wherein the spindle reciprocates between anextended position, a retracted position, and an intermediate position,wherein when the spindle is in the extended position, the spindlecounterbalance weights of the first and the second driven gears are inthe rearward positions, wherein when the spindle is in the retractedposition, the spindle counterbalance weights of the first and the seconddriven gears are in the forward positions, and wherein when the spindleis in the intermediate position, the spindle counterbalance weight ofthe first driven gear is in the upper position and the spindlecounterbalance weight of the second driven gear is in the lowerposition.
 21. The reciprocating saw of claim 15, wherein the spindlecounterbalance weight of the driven gear is a first spindlecounterbalance weight, the reciprocating saw further comprising a secondspindle counterbalance weight coupled to the driving gear such that thesecond spindle counterbalance weight is configured to rotate about theaxis of rotation in the first direction in response to rotation of thedriving gear by the motor.
 22. The reciprocating saw of claim 21,further comprising, a yoke coupled to the second end of the spindle, apin coupled to the driven gear and the second spindle counterbalanceweight for rotation with the driven gear and the second spindlecounterbalance weight, the pin having a first end and a second end, thefirst end of the pin coupled to the driven gear and the second end ofthe pin coupled to the second spindle counterbalance weight, wherein thepin extends through the yoke to couple the driven gear and the secondspindle counterbalance weight and to reciprocate the spindle withrespect to the housing along the longitudinal axis of the spindle inresponse to operation of the motor.